Polishing machines



Aug 2l, 1956 F. w. WHITEHEAD POLISHING MACHINES 5 Sheets-Sheet l FiledMay 5, 1954 Aug. 2l, 1956 F. w. WHITEHEAD 2,759,303

POLISHING MACHINES Filed May 5, 1954 5 Sheets-Sheet 2 F. W. WHITEHEADPOLISHING MACHINES Aug. 21, 1956 5 Sheets-Sheet 3 Filed May I5, 1954 El,i956 F. w. wHrrr-:HEAD 2,759,303

PoLxsHJ-.NG MACHINES Filed May 3. 1954 5 Sheets-Sheet 4 fly, 4

Allg 21, 1956 F. w. wHlTEHEAD 2,759,303

POLISHING MACHINES Filed May 3. 1954 5 Sheets-Sheet 5 Uni@ Sie@ 112e@ '02,759,303 PLTSHNGlVIHy :Nv I

Fiderick William Whitehead, Brist'ly'Ehglad; aissigiror to The'BristolAeroplane CompanyyLimitedyf-Bristol, England, a British companyApplication `iviiiy s, `1952i',-sciiti!N;22126599@J Claims priority,application Great Britain Mayo, '19532 This invention relates-tcinacliinsfer hierin-polishing by apl'vo'cess in'which the article robepoli lated while in contact with apad treated wi material intdr'fypowder, paste or liquidfsl'ispensron1 or witha sheetl treated withsuch-abrasive: mate'rialianii supported by a pad. The invention concernsmore particularlyn'iachines for use in polishing bladec'lile articlssnchasia'xal flow turbine blades.

According to the presentinventioii, a macliirl'e f'rise in polishingvthev two side surfaces of a blade-lilieafticl comprises two opposed'stacks of'pa'd liblders" whicht4 are spaced vapart atleast-far` enough`to eri'ableca 'padiiounted in'each holder and a blade-like articletobea'ccbiiimo'- datedibetween the stacks; a work holder frstipp'ortiiig" a blade-like article betweenthe tWo stacks ofpadiholder's withsuiheint space between thcv hltlelik iti'cleandeaeh'staclc to Venable atleast a pad mounted incliliol'dr to' be'accommodated between the holder' and the bladelike article, means forsupporting' said pad; lioldfs tliat'each pad holder is individuallymovabl'twrdsand away from a blade-like articl"wllei`1`-`it is lsiipfirtlby said wo'rl' holder, means' for' resilientlyA piessing' each padholder" towards-the otlieY s't'ck of p'adholds; and means forl linearlyoscillating saidwork lioldr ^tli'at it oscillatesa blade=like articlein'its" lngtliwise'diiectiil when the blad-lile articleis nlount'd`irltliewriholdr.

According: toia feature of the presentI invent Viit'he niacliinemayfurther comprise padsnioiitedoi iiieach pad holder each of which padshas an exposed f'e directed away from its holder, which eXpo'sed f'ce isShaped so that it together with the eiiposed faces of the otherf pads inthe same stack lie iniandprovid substantially the whole of a surfaceconforming' inl shape and extent to the whole of one side surface of ai'blade-like article lto be polished, the pads in one stack providing afsurface conforming to one side surface on* Stich' a bldlikeilalfilef al'th pfs'in life GhMSk-pb'viding a surfaceV conforming to the other sidesurface' o`f such al blade-like article;

During operation the exposed' faces ofi thefpads may come into contactwith" the side'isurfacesof a blad'elike article which is mounted? intheworkfholde'r, an'dfthis case it is preferred that the padsbecomposedffelte'd br'ou'sf material such` as wool felt.

Alternatively, however, the exposed'fa'cs offth pads may, duringloperation, be spaced fromthe sidesu-'rfaces off a blade`-like article,`which is mounted' said work holder; andinthis case the=machine furtherconlprisesfa pair ofi strips of' polishingmaterialg. one locate'd"roverf th'e exposed faces of the pads in" each-stadt; sof that when al'nladelilce article isf mounted" ini aE work\holder there isy a" stripof polishing material: sandwichedi betweenf the blade-like articleanclfeachsta'ckl of pads;

According: to f another featui'e" of: the'v` presenti' invention i eachofl the pads whenT mounted' in itsf holdermay have -itsaexposedfacesresilie'ntlyv mova'blefwitlil respect to' the holder. This may beachieved by making;v the'fpads of resilient material and/ or byproviding for the mounting Tice.,

off'each pad iii-its holder in a resilient manner; y Thus accordingtanotherfe'ature of the presentiinventine'ach pad hold may have' meansfor supporting tlie'end's of aresilienttbe'amor the like on which'itspad ismdunted, said' beam leildvsupport means being arrangedV to supportthe beam' a't'righ't angles tothe lengthwisev direction of 'ablade-like'article which is mountedinthe :work hl'del'. Th'epad'swhen'mounted onresilient beams are enabled tdwrpa'l'orid the curved proble of 'i anaiiialfowitrbine bladeand' this helpsto maintain lan lequal"bearingpressure over 'the whole exposed faceof-thepad. Prefi erablythe're'silient beam comprises a sti'lf'cdiledfspring which passesthrough'a bore" in tliepad; and which has its end pri'ecting from the'pad and retained 'in seat# ings intliepadholdel. l

Itis preferred'th'at at leastone cit-thev stacks of pad lioldesfisbdilymovable in relatioh'to 'the hlder te ahlinperative position tofacilitate theV rnduntiiig f yajbladz'ililcearticle inthe machineand'vaflsoitsrefnioval ther'frc'rnf.- In practice, cach stack of pad`holdersv is vrnofune onta separate supportaiid'inev of thesn'pportsi-'carri'cd in sh'dc sc a's-tc'bc 'nicv'ablc away ffcin'tn'c "other of'theV supports when it isj required "tomol'int a blade'flike" article inthe machine or remove' ablade'- lilcccfticlc from thc-machine. Y ,p

Preferably means is provilcdiforirnpa'rting'te 'thegitfirk helder'simultaneous oscillation' tjnibve' a1 Blade-like article, when-itissupported fronitlie' holder, in the` direction otitsfwitlth as wellE asiii-the directihcf its length, so that the 'rnpl't'hiotionimparted ttlie article'is o'f a'A rotary o'r wa'vy nat're. v y l It isf: also`preferred that said pressing rlea'nsl act on Veach -pdr' holder throughla pivot' itt/hieltI allows' the pad lielde'r tof tilt, said pivot' beingarranged with its* aiiis parallel to the lengthwise: direction of l aiblade-like article when it is mounted in thek work lolde'r'. pivotallows th'e'pa'd holder to tilt'to niain'tain'its padfcr'aiiiinterpos-edstrip f polishing materiali in'= contact with' tlie Whole Width Of" theblade-like article'.

In the preferred machine according to the invention caehfpadlhold-er'is'pivoted te an aint whichliirtiirh is pivotedabcut an'faxis' lying. in anplne infwllch the iiican planeI between the I side surfaces` ofl theblade-like `article lies when the article is snppc'rtedfrrh the weinli'ltiejr, thefpivtaxes of the'padll'iolde'r and'l ofi tlie'arni'extendiiig parallel to thelengthwise direct'in df thearticle When" it'is Supported ill the Work holder; This is db'le softhat` they surfacesof the pads'approa'cliithe bladelike article: as nearly as possiblenormallyto' itsi's-face's;

machine irl accordance with' thinverl'tionff us'ein polishing the frontand baclcsurfae'es' of axialE flowl turbine; blades" willV now be'described by' way" of example with reference to the accompanying'drawings' inrwhich':

Figure l isfav front elevatio'nof` themachineiwitliicertainpartsrenicvedfor thesake'dfclaity; Y i

Figure' 2' is side elevation" of! the' machine shown' in Figure l, andshowing a tubine bldel support'edf firn the work holder, Y

Figure 4I is apartial elevationalf cross-section o'nI line 4-#4-'0fFigure 3 arid Figure 5A is a View of Figure 3' in thel direction ofarroWf Si Referri'ngi to Figures. l and 2" off the drawings", themachine' comprisesla' casing lil:l upon which a table is mbunted,thelieighty of which is adjustable? by niansdf ab pair o'fvertical=slidesf 1'3l 'in' which"y the? tableslppbti'ng structure 14is-bolted; The Weiglitof' tli'e table-isI balz'znced-byl` a pairl ofchains I5; which pass? oyl a'vr pa'iiof pulleys 16 mounted within thecasing 11, and a number 3 of weights 17 suspended on the end of thechain opposite to that connected to the table.

The machine has a workholder 18 disposed above the table 12, in which achuck 19, to grip the root of a blade 10, may be mounted. The workholder 18 is forked and carries a horizontal pivot 18a (see Figure 2),upon which a chuck carrier 1812 is pivotally mounted. The carrier 18b isprovided with a slot 18C (Figure l) to receive a collar-stud projection19a on the chuck such that the chuck may also pivot about thelongitudinal axis of the blade 10, the blade projecting verticallydownwards as can be clearly seen from Figure 2. The chuck 19 issupported for movement vertically and transversely approximately in themean plane of the blade 10, in transverse and vertical slides 20 and 21respectively.

These movements are controlled by the setting of two eccentrics, one 22associated with the transverse slide 20 and the other 23 associated withthe vertical slide 21. Connecting rods 24 and 25 connect the eccentrics22 and 23 with their respective slide blocks. The eccentrics are ofadjustable throw and are driven by a single electric motor 26 (seeFigure 2). A pulley 27 is mounted on the motor shaft 2S and through belt3l) drives a pulley 29 mounted on a shaft 31, upon the opposite end ofwhich the eccentric 23 associated with the vertical slide 21 is mounted.For each reciprocation of the transverse slide 20 there are preferably anumber of reciprocations of the vertical slide 21 so that the totalmotion imparted to the chuck 19 is of a rotary or wavy nature; forexample, for polishing aluminum blades the preferred ratio isapproximately :1, while for polishing steel blades the preferred ratiois approximately 8:1. It is therefore necessary to provide a reductiongear box 32 to obtain the desired ratio. A pulley 33 mounted on theshaft 28 drives an input pulley 34, associated with the reduction gearbox 32, by means of a belt 35. A gear wheel 36 on the output shaft ofthe reduction gear box drives a second gear wheel 37 drivingly mountedon one end of a shaft 3S, the other end of which carries the eccentric22 associated with the transverse slide 20.

The blade is mounted in the chuck 19 so that the mean plane of the bladelies approximately transversely of the machine, as seen by an operatorstanding in front of it.

Referring more especially now to Figure 3, the machine table 12 supportsa rear part 39 which is fixed thereto by set screws, and a front part 40which is slidable to move forwardly or rearwardly (i. e. towards or awayfrom the operator). This movement is controlled by a pneumatic jack 41(Figure 2), the plunger 42 of which is connected to a slide 43 uponwhich the front part 40 is mounted. Parts 39 and 40 each support a stackof pad holders generally indicated at 44 and 45 respectively, the twostacks being brought together on operation of the pneumatic jack 41 (i.e. the front part 4t) is moved towards the rear part 39) and stacks 44and 45 (complete with pads) co-operate to polish the front and rearfaces of the blade 10 when it is reciprocated between them.

When it is required to remove the blade 10 from the machine, the frontpart 40 is moved back towards the operator by operation of the pneumaticjack 41 to an inoperative position.

Referring now to Figures 3, 4 and 5, spaced from the leading andtrailing edges of the blade 10 and lying approximately in its mean planeare two vertical shafts 47 and 48 carried respectively by the front andrear parts 40, 39, and on each shaft is journalled a stack of arms 49and 50 respectively each arm being L-shaped. The arms are journalled atthe extremities of their shorter limbs and the longer limbs of the armsof the two stacks extend transversely of the machine in oppositedirections respectively behind and in front of the blade 10. Theextremities of the longer limbs are supported by guide posts 51 and 52carried by the respective front and rear parts 40, 39 and provided withspaced grooves 53 in which the extremities slide horizontally. In themachine being described, nine such arms in each stack are providedspaced over the full height of the working part of the blade 10.

Opposite the middle of the width of the blade 10 each arm 49, 50 isconnected by a pivot pin 54 to a pad-holder 55 comprising a blockprovided with a groove 56 in one face S7 to receive the arm, and with asubstantially boxlike recess 58 in the opposite face 59 to receive arubber pad 60 which is greater in width than the blade at the chordwisesection at which the pad is positioned. The pivot pins 54 have theiraxes parallel to the lengthwise direction of the blade 10 when it ismounted in the chuck 19. Each pad 60 and its associated pivot pin 54 areretained in place by top and bottom plates 105 secured to the block bycountersunk screws, the total thickness of the blocks and cover-platesbeing slightly less than the spacing of the arms 49, 5t) to provide asuitable working clearance between adjacent pad holders 55. As will beseen from Figure 4, the intermediate covcr-plates 105 are made very thinso that the exposed faces S9 of the pads later referred to composesubstantially the whole of a surface corresponding to one side surfaceof the bladc 10.

Each rubber pad 60 is also retained in the recess 5S by a stiff coilspring 61 which extends transversely through the pad approximatelyparallel to the mean plane of the blade 10 and at right angles to itslengthwise direction, and tits in seatings on either side of the recess58. The spring thus acts as a resilient beam supported at it ends by theblock. In this Way a certain wrapping eifect of the pads 60 around thecurved profile of the blade 46 is obtained, this helping to maintain anequal bearing pressure over the whole exposed face of the pad. Toincrease the resilience of the pad a piece of sorbo rubber, i. e.,rubber having a cellular sponge-like quality, may be inserted in therecess 58 behind the pad.

The exposed face 89 of each pad is shaped to conform to the profile ofthe blade 10 at the particular section at which it is located. Therubber pads 60 of the front part 40 are mounted with their exposed faces89 directed away from their holders and facing the exposed faces of thepads 60 of the rear part 39, which are also directed away from theirholders, and the exposed faces of each stack of pads lie in a surfaceconforming in shape to the whole of the front and back surfaces of theblade 10 respectively.

The uppermost rubber pads 60 and lowermost pad bolders 55 of each stack44, 45 are provided with metal pins or spikes 9h for supporting stripsof felt constituting polishing pads 91, one over the exposed faces 59 ofeach stack of pads 6i). lt will also be seen that the top and bottomcover plates MP5 respectively of the top and bottom pad holders 55 ofeach stack are each provided with a hinge clamp 92 for securing a stripof emery cloth 95 over Athe felt pads 91. The emery cloth is used forpreliminary polishing and is removed to permit finish polishing by thefelt pads 1 employing a suitable abrasive material. Both the emery clothand felt pads 91 are somewhat Wider than the blade 10 so that theytogether wrap completely round it.

To allow the pad holders 55 to tilt about their pivot pins 54 andthereby reduce the deformation of the rubber and felt pads necessary tomaintain the faces of the felt pads (or the emery cloth strips) incontact with the whole width of the blade, the arms 49, 5t) do notextend to the bottom of the grooves 56 in the pad holders 55, theclearance preferably being increased with distance from the pivot pins54 by suitably tapering the arms 49, 50 as shown in Figure 3. Towardseach end of each groove 56 a coil spring 68 is suitably seated in thegroove, at right angles thereto, and bears at its opposite end on thearm so that the pair of coiled springs, one on each side of the pivotpin 54, serves to align the pad holder with respect to the arm.

b ffolritedupon'each p'art 39,- {10 between tlieveptical shaft '47,48'andthe guide post 51,V S2 is a block 63the stacks of arms 449, 50 lyingvbetween the twp blocks.l Each block hjas one horizontal bore 64'(seeFi-gure4) in the plane or, and vdirected toward-s,` each of the L'shaped arms 49 or 50 ofy'the adjacent stack 44 or'45: Each-"bore 64 is'provided at'its end remote fronithearm'with a screw Ithreaded abutment65` for a `coil spring` 66, the other end of which bears upon a'plunger67 having-v4 an end projecting from the block 63 into contact with therespective arm' and -constitutingpressing meanswto press the arm towardsthe other stack ofarms. Adjustment ofthe abutments 65 thus permits thepressure'swith which the pads are applied to the blade 46, eitherdirectlyor indirectly, to be set individually. K l

When operating the machine asfuipt` of emerycloth 9.5 isattachedrrtoboth `stacks *of pad holders 44,A 4S overthe felt pads 91. A blade isinserted inthe chuck 1-9 and the movable part 40 is moved into" itsiworking position bythe pneumatic jacle 41- so that the blade-isgrippedbe `tween. the opposed strips ofemery cloth.= The driving motor26 is started to oscillate the blade vertically and transversely. Duringthis movement the pad-holders 55 `tilt slightly about their pivot pinsv54V so thatunitorm polishing-pressure' is' maintained over `the whole'ysurface of the' blade. This is'continued for a` desired time to completepreliminary polishingwhereupon the machine* is stopped,` the part ttlmoved away from' part 39and the blade is removed.:` The emery clothwillserve-'topolish a large number ofl blades before requiring- Yrenewal.-For ltheiinalpolishing process the emery cloth is'removed, the blade isimmersed in a viscous mixture offoil and powdered'abrasive such as emeryso as to apply athin coatingofA the mixture toit, and' is re-inserted inthe chuck. The movable ,part @dis againmovedY into its workingpositionvso; that the blade is grippedbetween the two opposed felt pads 91V andthe machine'is started asf before to perform'the final polishingoperation, I

'Fh-e unit lltlwithithef dial o-n the upper left-handside ofFigure lis'f'a lcycle'ti'rner which mayfbesetby adjustmentof its'pointer to`=adesired cycle time sothat the ma'- chine isaut'cmatically/ stopped onm(,:o'mplet'ionl of the" cycle'. "Fhge'llnitltl isV self resetting` Thedi'al ,1011 onthe right ofvv FigureY 1 records` the air pressure foroperatingI the pnenmaticfjack 415 The:eccentrics`22f, 2-3, theconnectingvrodsA 2'4, 25,b and the" slides 2d, 21- arer covered` b'y afprotectivecasingpr guard 1in-removablyattached to the casing-.1las at103.

The pads'oi), instead of beingmade of rubber, may' be coh'iposedf'ofwool `felt; in which case they pads may bear directly' onthe'bl'adeduringa final polishingoperation-` It is'preferredto'have an interposedpolishingpad such a's 91I however, or' an: interposed strip' of feltclamped acrossthc'expose'd faces of--thepads in eachstacl't like theemery cloth strips which have been described,-ij`becausle the gapbetween the adjacent pads 60 is then bridged, giving a moreg ev en'fpolishing: with 'ai *smallverti'caloscillation of the blade. v n

The use of rubber pads 6l) is'ualso preferred, although a fait 'parSacias or canne usd'lovrfea'pads eorbedse rubber pads have a greaterdegree of resilience then felt pads. if felt pads'dtl'are used, theseare mounted on tanlsversesp'ings 6-1 whichfgifveth'e'ifz certain-larnount of resilience in relation to their holders which is essential.The need for mounting the rubber pads 60 on springs 61 is not, however,necessary, and instead the rubber pads 6i) may be doveatailed into theirholders, the resilience of the pads themselves being relied on to givethe necessary resilience between the exposed faces 89 of the pads andthe pad holders.

I claim:

l. A polishing machine for polishing the two side surfaces of ablade-like article, said machine comprising a base structure, a workholder carried from said base structure for supporting a blade-likearticle, the side surfaces g, of which are to be polished', inaworkpiecepositionwith the lengthdimension of the article in'a'gixedAV directionrelativelyto said supportj structure and withv said` side surfacesexposed-for polishing bythe machine; meansforlinearly'oscillating-fsaidworkholder in saidftixeddirection, two opposedstacks of pad holders carried by saidbase struoture,.-on e on `eachsideofsaid workpieceposition, each of said stacks of pad'holders comprisingasupport means; a plurality'of padholders carried by said support meansso -as to be distributedin" sideby side relation in'said xed' direction4and-so as to be individually. movable-to'- Wards-andaway 'fromthe"workpieee-position,A andfor'each pad holder a resilient meansengaged'between-the pad holdei and `anabutment carriedZ -fro'rn 'saidlsupport strut:h Iture for urging the pa'dy holder individually towardsthe workpiece position,4 al polishing-'pad mounted in 'each 'pad holder,each padlhaving ani exposed'A face' directed away from itsvlrolderftlreirposed faces or the padsinf onestack forming substantiallythe whole of a surface' conforming in 'sh-'ape andfextent tothewhloleo'fone sid'e'su'rface -of a blfadeL-l'ik'eaticle to 'be' Ypolished, an'dithe'f eXps'edfaces ofthe'padis i the oth'erstaclc formingsubstantially the Whole"o'iaL surface C'E'J'Iforg5 ini shape andeXtent't the whole of the other sidesurface o`f`y such' ai blade-likeartibljsidst'acks" of pad holders rbeing spaced apart atleast""fair"enough to'enabl" Ya bladedil't'eYI 'article mounted ins'aid'worlhol'de to be'acomiiodated'betwen the stacks with theblade-like article gripped between' two stacks'of padslwithdiieofitsside surfaces facing towards thep'ads i'n loieofthe"stacks andthe other kof its` sidef surfaces'facing ftvafds'the pads rheother ofthe stacks;

2L' machneas" claimed in claim l, wherein, duringoperation,.thefepo'sed'facesof the pads are'` spaced from theside'surfaes'of bldelkearticlewhn' it is supported from sdiwork' holder,themac'h'inefurhr 'compris g aiv pair of strips of polishing materialone located oveall theeq'n'o'sedVv fesofthe' pads'in" one'y of the"stacks and lthe o'ther'loc'ated'over'all the"e` l ps`edfaces of thep'ad'sl in theother offthe' stack'sfso'lthat whena blade-likeart`icleis'rnoun'ted'in Ithe work holder therev `is a strip yof polishingmaterial-i sandwiched between" the A blade-like article and each stack'ofpads.` l I 3 A machine as claimed` in claim/1, wherein 'each padholder" has means for supportinggthe ends ofva resilient beam on whichits pad is mounted, said beam endsupport means beingparranfged tosupport'the beam at right angles to'the lengthwise directiorrofabladelike article which yis supported-fromthe work holder.

4.' A"1nac'hineas claimed in claim 3, wherein said-re sifintbeanrcompris'e's astiffcoiledspring which passes through a bore intherpad; vand which has its ends projecting from the pad'n andi-retainedinl seatingsf-in thepad holder:

5. Apolishi'ng machine for polishingfthe` twoside'su'rfaces ofl a*bladedike article, said machine" comprising@ a base structure; 2r-'workhold'er'carried from saidl base st'ructur'efor supportingabladeililcearticle,` the sidesurfaces of which are to be polished, in aworkpiece-position with the" length dimension of' the article in` aAiixed' direction relatively 'to said support structureand-withA saidside surfaces exposed for polishing by the machinefmeans'for linearlyoscillating'tsaid'work-holder in'said x'ed direction, two" opposedstacks off-padI holders carried;4 by` said Hasestructure, one on' eaphsideof-Y saidv workpiece posi'- tio'iryeach'of saidstacksofpadfholders-comprising.asup port means, a plurality of pad holderscarried by said support means so as to be distributed in side by siderelation in said fixed direction and so as to be individually movabletowards and away from the workpiece position and for each pad holder aresilient means engaged between the pad holder and an abutment carriedfrom said support structure for urging the pad holder individuallytowards the workpiece position, said stacks of pad holders being spacedapart at least far enough to enable a pad mounted in each holder and ablade-like article mounted in said work holder to be accommodatedbetween the stacks of pad holders with the blade-like article grippedbetween the two stacks of pads with one of its side surfaces facingtowards the pads in one of the stacks and the other of its side surfacesfacing towards the pads in the other of said stacks.

6. A machine as claimed in claim 5, wherein at least one of said stacksof pad holders and the abutments of the resilient means of said one ofsaid stacks of pad holders are movable together in relation to the workholder to an inoperative position to facilitate the mounting of abladelike article in the machine and also its removal therefrom.

7. A machine as claimed in claim 6, wherein said one of said stacks ofpad holders and the abutments of the resilient means thereof are mountedon said base structure in a slide so as to be movable away from theworkpiece position when it is required to mount a blade-like article inthe machine and to remove a blade-like article from the machine.

8. A machine as claimed in claim 5, wherein means is provided forimparting to said work holder a simultaneous oscillation to move ablade-like article, which is supported from the work holder, in thedirection of its width as well as in the direction of its length.

9. A machine as claimed in claim 8, wherein each of said oscillationimparting means includes an adjustable throw eccentric, said eccentricsbeing drivable from a common motor.

l0. A polishing machine as claimed in claim 5, wherein said pressingmeans act on each pad holder through a pivot disposed so as to liesubstantially centrally of the width of a pad mounted in the holder,said pivot being arranged with its axis parallel to the lengthwisedirection of a blade-like article which is supported from the workholder and allowing the pad holder to tilt about said axis.

ll. A polishing machine as claimed in claim 5, wherein each pad holderis pivoted to an arm by means of a pivot disposed so as to liesubstantially centrally of the width of a pad mounted in the holder andthe arm is in turn pivoted about an axis lying in a plane in which themean plane between the side surfaces of a blade-like article lies whenthe article is supported from the work holder, the pivot axes of the padholder and of the arm extending parallel to the lengthwise direction ofthe article when it is supported from the work holder.

l2. A polishing machine as claimed in claim ll, wherein a pair ofsprings is provided between each pad holder and the arm to which it ispivoted, said springs being positioned one on each side of the pivotconnection between the pad holder and the arm and acting on the padholder to align the pad holder with the arm.

13. A polishing machine as claimed in claim l1, wherein the arms of thepad holders in each stack are pivoted i about a common axis lying at oneend of the arms, the arm axes pertaining to the respective stacks lyingon opposite sides of the work holder, and wherein eac'h arm is supportedat its free end by guide means on which it is able to slide.

14. A polishing machine as claimed in claim 13, wherein each arm isL-shaped and is pivoted towards the free end of one of its limbs, thefree end of the other of its limbs being supported in said guide means.

15. A polishing machine as claimed in claim l1, wherein said pressingmeans each comprises an adjustable spring-loaded plunger bearing uponone of said arms.

16. A polishing machine for polishing the two side surfaces of a twistedaerofoil sectioned blade, said machine comprising a base structure, awork holder carried from said base structure for supporting a blade, theside surfaces of which are to be polished, in a workpiece position withthe length dimension of the blade in a fixed direction relatively tosaid support structure and with said side surfaces exposed for polishingby the machine, means for linearly oscillating said work holder in saidxed direction, two opposed stacks of pad holders carried by said basestructure, one on each side of said workpiece position, each of saidstacks of pad holders comprising a support means, a plurality of padholders carried by said support means so as to be individually movabletowards and away from the workpiece position, and for each pad holder aresilient means for urging the pad holder towards the workpieceposition, said stacks of pad holders being spaced apart at least farenough to enable a pad mounted in each holder and a blade mounted insaid work holder to be accommodated between the stacks of pad holderswith the blade gripped between the two stacks of pads with one of itsside surfaces facing towards the pads in one of the stacks and the otherof its side surfaces facing towards the pads in the other of saidstacks.

17. A polishing machine for polishing the two side surfaces of a twistedaerofoil sectioned blade, said machine comprising a base structure, awork holder carried from said base structure for supporting a blade, theside surfaces of which are to be polished, in a workpiece position withthe length dimension of the blade in a fixed direction relatively tosaid support structure and with said side surfaces exposed for polishingby the machine, means for linearly oscillating said workholder in saidxed direction, two Opposed stacks of pad holders carried by said basestructure, one on each side of said workpiece position, each of saidstacks of pad holders comprising a support means, a plurality of padholders carried by said support means so as to be individually movabletowards and away from the workpiece position, and for each pad holder aresilient means for urging the pad holder towards the workpieceposition, a polishing pad mounted in each pad holder, each pad having anexposed face directed away from its holder, the exposed faces of thepads in one stack forming substantially the whole of a surfaceconforming in shape and extent to the whole of one side surface of ablade to be polished, and the exposed faces of the pads in the otherstack forming substantially the whole of a surface conforming in shapeand extent to the whole of the other side surface of such a blade, saidstacks of pad holders being spaced apart, at least far enough to enablea blade mounted in said work holder to be accommodated between thestacks with the blade gripped between the `two stacks of pads with oneof its side surfaces facing towards the pads in one of the stacks andthe other of its side surfaces facing towards the pads in the other ofthe stacks.

References Cited in the file of this patent UNITED STATES PATENTS1,490,631 Newkirk et al. Apr. l5, 1924 FOREIGN PATENTS 1,948 GreatBritain Aug. 28, 1855

